The gemetry, ionic interactions and rotational mobility of phospholipids having differing types of polar head groups are to be examined by laser Raman spectroscopy. Our preliminary Raman temperature studies of phospholipids and Raman temperature studies and normal coordinate analyses of small model molecules show that Raman bands due to the phosphate and amine moieties can be used to estimate conformation, environmental interactions and rotational freedom of phospholipid polar head groups. These head group Raman bands plus the hydrocarbon side chain Raman bands will be used to determine the detailed behavior of phospholipids with varying head groups in temperature-dependent phase transitions, water binding, cation binding, hydrogen ion binding, and mixed-lipid phase transitions. The lipids to be studied are phosphatidyl choline, phosphatidyl ethanolamine, phosphatidic acid and phosphatidyl serine.